THE 




BY 

T. EGLESTON, Ph.D., 

If 

NEW YORK CITY. 






A Paper Read before the American Institute of Mining 
Engineers, at the Boston Meeting, February, 1883. 






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AUTHOR’S EDITION. 
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TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS.J 




£-A- 


WE METHOD OE OOLLEOT1NO FLUE-DUST AT EMS OH 

THE LAHH. 

BY T. EGLESTON, PH.D., NEW YORK CITY. 


(Read at the Boston Meeting, February, 18S3.) 

The importance of condensing the gases which escape from fur¬ 
naces so as to save both the fine particles of ore carried off mechani¬ 
cally and those which are volatilized, has for a long time occupied 
the serious attention of metallurgists in all parts of the world. 
It was my good fortune during the last summer to visit the lead 
and silver works at Emsi, near Coblentz on the Rhine, and through 
the politeness of Mr. Freudenberg, General Director of the works, 
to study in detail their methods of condensation, and to receive from 
him the important results which have been obtained through a series 
of experiments lasting over a number of years. I have thought that 
these results would be of great interest to the members of the Insti¬ 
tute and to other metallurgists in the United States, and I have, 
therefore, with the assistance of Mr. Freudenberg, prepared a care¬ 
ful, detailed description of the construction of the flues, as well as 
an account of the various experiments which have been made with 
them, and the conclusions arrived at as the result of these experi¬ 
ments. 

It may be said, in general, that the reason why so little atten¬ 
tion has been paid in the metallurgical works of the United States 
to the collection of flue-dust, is that we are not generally aware of 
the large amount of material carried ofl‘ by the gases. This is owing 
partly to the fact that little or no attention is paid to the subject, 
and also to the fact that the assays, which are almost invariably 
made in the dry way, show a result so much below the real contents 
of the ore that the loss appears smaller than it really is. If assays 
were always made in the wet way the result would be quite different, 

1 


2 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


and probably vve would have long ago given attention to this sub¬ 
ject of flue-dust. 

All the experiments that have been made in the direction of 
saving the materials carried off by the gas may be comprised in 
two categories,—those in which attempts have been made to col¬ 
lect the dust by means of water, and those in which water has not 
been used. The condensation of gases by means of water is at best 
a very rude method. Experience has shown that both solid and 
gaseous products, even when not under the influence of pressure 
or of high velocities, may traverse considerable depths of water 
without change and with almost no condensation. Water conden¬ 
sation has been used in this country to some extent, but its results 
have always been unsatisfactory, both because the material which 
is so condensed is very difficult to treat, being collected as a liquid 
mud, which when dry is in the form of an impalpable powder, 
and because the water supply in most of the places where the works 
are situated is very limited; so that at the present time most of 
the serious experiments that are being made are conducted alto¬ 
gether without water. It becomes at once a matter of the first im¬ 
portance in these experiments to know whether great length or great 
volume of flue within a given extent, or great surface in a limited 
volume, is better for this purpose of condensing the gases. The 
experiments made at Ems are quite conclusive in regard to this 
question, and show that great surface is the most indispensable re¬ 
quisite. 

It will generally be found that three things are required in 
any method of condensation. The first, and what is generally con¬ 
sidered the most important of these, is the settling and complete 
separation of the line particles of ore carried off mechanically by the 
draft. The second, which in all works where the precious metals are 
treated is much more important, is the condensation of the material 
which is volatilized or carried off in a gaseous condition. The third 
is the retaining of all the particles once at rest in the position where 
they have first fallen in such a way that they may afterwards be 
collected without loss of the precious metals or danger to the health 
of the workmen. To the latter condition but little attention has 
been paid in this country. I have formerly had occasion to refer 
to a very ingenious method adopted by the Pennsylvania Lead 
Works,* for holding the precipitated or condensed material in the 

* Trans. Am. Soc. Mechanical Engineers, Vol. i., p. 8. 

£ H 




METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 3 


position where it fell, which, so far as I know, is the only experi¬ 
ment of this kind made in this country. The question of choice 
• between very long flues and very wide chambers seems to be settled 
definitely, as we shall see by the experiments made in the works at 
Ems, the conclusion being general that a maximum of surface, with¬ 
out special reference to volume or leugth, is what is required, and 
that this maximum of surface can be better gained, so far as the con¬ 
densation is concerned, and also more economically arrived at as to 
cost, by the arrangement which is there used. 

The experiments made for condensing the materials contained in. 
the gases were commenced in a systematic way in the year 1874, 
when, with the object of obtaining volume, both systems, that of 
short wide chambers, and that of long narrow flues, were con¬ 
structed, in order to ascertain what Should be the principle adopted 

in the future construction of the works. In order to understand the 

% 

experiments thoroughly, a ground plan of the smelting works, and 
of the flues, and a profile of the flue from its point of starting in 
the works to where it finally terminates in the chimney which dis¬ 
charges the gases into the air, are given on Plate I. 

The Ems Lead and Silver Works are composed of two separate 
establishments. The one which is nearest to the famous watering- 
place is the mechanical preparation or ore-dressing works, which is 
one of the largest, the most complete, and also one of the best known 
in Europe, but with which we have nothing to do in this article. 
The mines, the smelting works, and.a small part of the mechanical 
preparation works are situated about four miles distant in a valley 
running at right angles to the valley of the Lahn, through which a 
small stream runs. The mine and part of the crushing and select¬ 
ing works are situated on the eastern side of this stream ; the smelt¬ 
ing works are situated on the west bank of the same stream. These 
latter consist of a series of buildings containing the furnaces and 
storehouses, built upon a plateau several meters above the stream, 
at the foot of a high hill which next the works is very steep, but 
which, after passing Station 22 (Plate I.), rises more gently. Lead¬ 
ing away from the works up the hill, are a series of flues of various 
sizes, the first part of which runs along an old road up to the first 
chimney at Station 22, and from there goes directly over the hill to 
the highest chimney at Station 47. The U-shaped part of the flue 
e,f, g, h, on which the shaft and roasting furnaces are situated, is 
joined to the furnaces by means of short flues. The plan shows the 


4 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


position and arrangement of all of these buildings and flues. The 
construction details of the flues at different points will be given later. 

The main flue is 1700 meters in length ; counting all its branches, 
its total length is 2271.48 meters. The greatest section of the flue 
is 4.512 square meters. Its total wall surface is 18.060 square meters. 
Its highest point at Station 47 is 178 meters above the floor of the 
furnaces. At this highest point it enters a chimney whose section 
at the bottom is 2.47 meters and at the top 1.80 meters, and whose 
height is 45 meters, its top being 223 meters above the furnaces. 
The ventilating flue N, and its chimney L, which were formerly used 
for ventilating the shaft and cupel furnace house G, and the flue 
from the roasting stalles, which ends in the chimney at Station 22, 
have no connection with the main flue. The short and steep flue 
a 6, with its arm c d , connects' the shaft and cupel furnace house, 
and also some of the roasting furnaces, with the condensing cham¬ 
ber at Station 16. The gases enter on the southerly side, in the 
compartment I, Fig. 10, Plate II. These gases move towards the 
northerly side; those in compartment II towards the southerly 
side. The flue ef',fg, hi, K, connects the other roasting furnaces 
with the main flue also at Station 16, but follows around an old 
road going gradually and with an irregular curve up the hill, and 
empties its gases into the compartment III of the condensing cham¬ 
ber at i, Station 16. The gases enter on the northerly side in the 
compartment III, join those in compartment II, and enter the main 
flue at Station 15. 

In order to make the description of the process quite clear, sections 
of the flues at different parts of its course have been given, both to 
show their methods of construction and the means used for obtaining 
both volume and surface. 

Fig. 1, Plate II, is the flue leading from shaft furnace No. 2 to 
its union with that leading from No. 3, and from the point where 
the flues of Nos. 2 and 3 join, to the main flue; and also the flue 
leading from shaft furnace No. 4 to its union with the flue leading 
from shaft furnace No. 3. 

Fig. 2 is the flue leading from shaft furnace No. 3 to the union 
of the flue with that from shaft furnace No. 2. 

Fig. 3 is the flue from shaft furnace No. 1 to the main flue. 

Fig. 4 is the flue from shaft furnace No. 5 to the main flue. 

Fig. 5 is the flue from the point of union of the shaft furnace 
flues to the condensing chamber at Station 16. 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 5 


Fig. 6 is the flue from the six most southerly roasting furnaces to 
the main flue, and also the flue from the dressed-ore storehouse to 
the two most northerly double roasting furnaces. 

Fig. 7 is the flue from the two most northerly double roasting fur¬ 
naces .to the end of the dressed-ore storehouse ; also the flue which 
runs by the most northerly roasting furnaces. 

Fig. 8 is the flue of the most northerly roasting furnaces. 

Fig. 9 is the flat flue of the most northerly roasting furnaces. 

Fig. 10 is the first condensing chamber on the top of the first 
incline at Station 16. 

Fig. 11 is the flue from the condensing chamber to the outside of the 
old chimney at Station 22, and from here to the edge of the woods, 
and from the edge of the woods to the flues connecting with the 
chimney at Station 47 on the top of the hill; also the flues connect¬ 
ing with the chimney. 

Fig. 12 is the condensing chambers X and Y beyond the chim¬ 
ney, but connecting with it. 

The flues in the interior of the shaft furnace building are made of 
sheet iron-plates 1J millimeters thick, and are hung 30 centimeters 
above the throat of the furnace. Figs. 1, 2, 3,* show some of the 
flues which lead from the cupel furnaces. The same kind of flues 
are used in the desilverization works, but they belong to their own 
system of condensation, and do not connect with the main flue. Some 
slight changes in these dimensions are occasionally made on account 
of local circumstances, but the size of the larger part of them is one 
square meter. The lower part of Figs. 1 and 2 have triangular 
projections, which have a base of two meters and are one meter high. 
All these pointed chambers have doors at the end of each incline, so 
as to make it possible to clean each pocket while the furnaces are in 
work. In order that the dust may not inconvenience the workmen 
while they are being cleaned, a sheet-iron-pipe 40 centimeters in di¬ 
ameter is put underneath them. Into this pipe another one which 
is conical at its upper end, fits loosely so that it can be moved up and 
down. This is put under the triangular pocket, the cone shoved up 
under it, the door opened, and the dust allowed to fall down into a 
receptacle made for the purpose, without interfering with the work¬ 
men. Iron flues connect with these pocket flues and conduct the gases 
to the main flue outside the building. By this very ingenious con¬ 
trivance the dust can be almost automatically removed from the 

* The exact location and position of each one of the figures is given in Table I., 

p. 10. 




6 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


flues, the cleaning of which would be more or less difficult or dan¬ 
gerous, without*’stopping the furnace, and a large amount of valuable 
material is taken at short intervals out of the gases before they pass 
into the main flue, where they would otherwise be obliged to lie until 
the end of the campaign.- 

The flues on the outside of the shaft furnace building are of mason 
work. They have different sections according to the quantity of gas 
which they are required to carry off. These are shown on Figs. 4 
to 9 and on Fig. 11. It has been found bv experience that the arched 
flues, which at first characterized the whole of the construction, al¬ 
though of an excellent shape for resisting pressure from the outside, 
do not stand well against internal pressure, and that cracks are 
made in them so frequently that they are now being abandoned. 
The flue with rectangular section, Fig. 9, is not subject to these 
objections, and this style of construction is now adopted in these 
works and elsewhere in Europe. The roof of this flue is made of 
old rails covered with brickwork, and is inclined on the outside to 
one side, so as to shed the water. The cost of construction of this 
kind of flue is much less than when it is vaulted and it has a much 
greater volume for the same height and superficial area, and while 
it is just as likely to be acted on by the gases it is much more easily 
repaired. As it is much lower, the dust falling from the top falls 
from a less height, and is not therefore so likely to be carried any 
great distance from where it fell. The cross section of the condens¬ 
ing chamber at Station 16 is shown at Fig. 10. The ceiling of this 
chamber is made out of old rails with cap bricks. Above this is a 
wooden roof made tight with pasteboard underneath the tiles. In 
every section of the flue, at convenient distances, man-holes are made 
for cleaning it out, and to facilitate repairs. These man-holes 
were formerly about 0.6 meter in diameter, and were made ex¬ 
clusively on the top. It has been found more convenient to make 
large rectangular openings on the sides which, during the working, 
are closed with a wall of thin brick, and made tight on the sides and 
face with mortar. These walls are easily torn down to allow of the 
men entering on the floor of the flue with wheelbarrows to clean the 
dust out, and greatly facilitate the repairs to the flues. The earth is 
now being removed from the sides where the construction makes it 
possible, for the purpose of making these inlets. This has been found 
also to reduce the temperature of the flue, a matter of considerable 
importance so far as repairs to the flue are concerned, for, especially 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 7 


with the arched due, when the temperature is either high or very 
variable the walls have cracked and required constant repairs, which 
has at times necessitated the stoppage of the works. Every care is 
taken to carry the drainage of the surface over the top of the due 
aud not to allow the collection of water at any point. The dues 
over this whole line are now generally very tight. As the earth 
which covers or is in contact with them is much warmer than that 
of the neighboring ground, the grass is much greener than at other 
points, a sufficient evidence that no large amount of leakage occurs. 
1 walked over the whole length of the due, examining its con- 
struction carefully, and was conscious of the escape of the gases only 
in one or two points, and that to no very great extent, and princi¬ 
pally in the arched portions of it. Repairs to such a due could not 
generally be made without shutting down the works. In one of 
the works in Belgium I saw a very ingenious device for repairing a 
damaged due without stopping the works. It consisted of a pipe of 
sheet-iron of the same section as the main due, washed on the in¬ 
side with a mixture of silicate of soda and sulphate of baryta. The 
part of the due .to be repaired was cut out, and this pipe substituted 
for it, while the permanent due was being rebuilt. This iron pipe 
was about one meter in diameter, of thin sheet-iron, and had resisted 
the hot sulphurous gases perfectly for several months. I carefully 
examined several sections of it, which showed no trace of oxida¬ 
tion or deterioration of any kind on the inside, and it was pierced 
only where acid waters had come in contact with the outside. But 

w 

for this ino-enious device the whole works would have had to be 
© 

shut down for several months. 

Up to the year 1877 the chimney shown at Station 22 was the one 
used for carrying off all the furnace gases. The due used up to the 
vear 1874 was torn down, as it was too small for the increased 
production of the works, and was replaced by a larger one, better ar¬ 
ranged for taking off the dust. In 1874 a large chamber was built 
next to this chimnev, but after some years it was abandoned on ac- 
count of the large amount of repairs which were required, and the 
chamber shown at Station 1(1 (Plate I.), and Fig. 10 (Plate II.), was 
then built. It was thought necessary, at the time it was constructed, 
to make an arrangement by which it could be cleaned very frequently, 
whenever the works should increase their production, and to have 
a cut-off, shown at b and k, so that the gases might be made to 
pass beside it into the main due while it was being cleaned. It was 


8 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


found, however, that the small quantity of dust collected made this 
unnecessary. 

In the year 1877, the chimney at Station 47, and Fig. 13, was 
built, and connected with the flue leading to it on October 1st of that 
vear. It was found necessary afterwards to increase the condensa- 
tion surface, and on October 1st, 1880, the two buildings (X and Y, 
Plate I.), and Fig. 12, Plate II., containing condensing chambers, 
built beyond the chimney, were added to the Hue. These build¬ 
ings are 100 meters long. Each one of them consists of an upper 
and a lower chamber, with two divisions in each, separated by 
a flat ceiling which rests upon iron rails. The roof is inclined 
at an angle of 35°, and is made of iron rails riveted together with 
angle iron. Tiles are laid upon this and the joints covered with 
clay. The roofing which was put upon the northern section did not 
stand well, and, in consequence, in the latter part of the summer, 
loam was laid over it, and this was covered with a second coating 
of beton. As sulphurous acid sometimes escaped from some of the 
other roofs, they were treated in the same way, and were then painted 
with tar. This kind of roofing does not appear to last very long, 
and is liable, on account of cracking, to require considerable repairs. 
When I visited the works, in September, 1882, the whole of the upper- 
part of the chamber (Fig. 12), had been put out of use, as the roof 
was leaking gas so badly as to render the works liable to heavy fines. 
A large amount both of volume and surface was thus lost at that 
point, but the surface was almost immediately regained by the system 
described further on. The chimney is shown at Fig. 13. It is 42 
meters in height above the socle, and its diameter is 2.47 meters in 
the lower part, and 1.80 meters above. As it was thought that this 
chimney might have a stronger draft than the proper working of the 
furnace would admit of, a movable damper was put in it (Fig. 13.) 
On the outside a quadrant was placed; an arrow attached to the 
axis moving over the quadrant shows exactly the angle of the 
damper in the interior of the chimney. When everything is working 
well, the angle is 45°. Before the addition of the chambers, X and 
Y, it was as low as 27°. The gas passes out of the main Hue at n, by 
an elbow at Station 47, and enters the under part of the southern sec¬ 
tion of the condensing chamber building X (Fig. 12); it passes from 
that to the upper part of the same building, and then, at p, to the 
under part of the northerly building, Y, then, at q , into the southerly 
part, and finally at r, by an elbow, r s } enters a section of the main 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 9 


Hue, which has been walled off just beyond the elbow n, and from 
there goes directly to the chimney. 

A number of experiments have been made to ascertain the tem¬ 
perature of the interior of the flues. It has been uniformly found 
that the temperature of the gases in the roof of the chambers was 
as shown in the table below: 


At Station 15, .......... 

« “ 94 

• ••••••••• 

35, at vi, ......... 

At entrance of last chambers, X, Plate I., and Fig. 12, Plate II., . 
Coming out from the “ Y, “ “ . 


136° C. 
119 
108 
89 
64 


Although the sum of the sections of the two flues ah , gh is larger 
than that of the main flue at Station 16, they are not entirely filled 
with gas, and it is therefore not full, and consequently the temperature 
on the bottom is always some degrees lower than at the roof. The 
difference between these two temperatures is greater as the tempera¬ 
ture of the gas is higher, and also as the height of the flue is greater. 
At Station 15, where the shaft furnace flue joins the main one, it 
was found to be 8° ; at the entrance to the chimney at Station 47, it 
was found to be 2°. The mean outside temperature varied during 
the days upon which these observations were taken, between 6^ 
and 10°. 

Table I, below, gives the dimensions, volume, and cost of the 
different parts of the flue, and the sections into which it has been 
found desirable, to divide it, for keeping the record of the action of 
the different parts of the flue. The cost has been given in marks. 
The value of one mark is $0,238. 


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10 METHOD OF COLLECTING FLUE-DUST AT EM8 ON THE LAHN. 


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METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 11 


The cost of constructing the flue was large in certain parts of it, 
on account of the difficulty of carrying the building materials up to 
the high ground where the flue was built. On comparing the cost of 
each part of the flue, it appears that the flat portion of Section IV., Fig. 
9, as well as the large condensing chamber buildings, X and Y, Fig. 
12, were the cheapest. It must be noticed, however, that two of 
the flues have nothing to do with the saving of the flue dust. One 
of these is the one which goes to the old chimney at Station 22, and 
carries the gases from the stalls used for roasting the lead matte. 
These stalls are used only a short time during the year. The other 
is the one used for the ventilation of the shaft-furnace house. 

Around each one of the five Pilz furnaces, one meter from its 
outside, and one and a half meters above the furnace-hearth, a sheet- 
iron cylinder two millimeters thick is placed. It is open below but 
closed above, and is joined to a pipe fifty centimeters in diameter. 
Each one of the pipes for the five furnaces passes through the charg¬ 
ing-floor. They meet together outside of the building in a flue, which 
leads to the chimney L at Station 13, which chimney is 18 meters 
high and 43.5 meters above the charging-floor. This furnishes suffi¬ 
cient draft to carry off the fumes. 

Table II. below, gives the results which have been obtained with 
the flues just described during seven campaigns. It gives also their 
length, interior dimensions, and cubical contents during the different 
periods of construction and change, and also the results which have 
been obtained by 100 meters in length, 100 square meters and 100 
cubic meters respectively. 


TABLE II. 


12 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN 


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METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 13 


In making the comparison of the material collected on every 100 
square meters of wall surface and that of every 100 cubic meters of con¬ 
tents, the first four campaigns are particularly noticeable, as in these 
the relation of the square meter to the cubic meter, that is, to the 
mean section of the flue, has frequently changed. When the flues 
were first built they were made, as they usually are elsewhere, narrow. 
Those more recently constructed, which have served partly to replace 
defective ones and partly for the increased production of the works, 
are made much larger than they formerly were. The mean section 
of the entire flue has in this way become constantly larger, so that 
when the old flues were finally destroyed the large section was taken 
as the normal one for the new ones. In the first campaign the sec¬ 
tion of the flue was 1.79 square meters; in the second, 2.16 square 
meters; in the third, 3.21 ; and in the fourth, fifth, and sixth, 4.Q8 
each. The only change in the seventh campaign was the insertion 
of 23,791.12 square meters of sheet-iron plates. Very little data 
can be given with certainty for the eighth campaign ; several acci¬ 
dents occurred, which made it necessary to make the gases exit at 
the chimney at Station 22, so that for some time a large part of the 
flue was not in use. The cleaning and transportation of the flue- 
dust was made in very rainy weather, which made the weight of it 
uncertain. For these reasons this campaign has been left out of the 
question. Making a comparison of the quantity of lead collected 
per square meter of wall surface in the first four campaigns, the table 
shows that the quantities were nearly alike and varied regularly in 
very small quantities, while, on the contrary, the quantity collected 
per cubic meter during the enlargement of the flue was considerably 
less. From this the conclusion may be drawn that the material col¬ 
lected under such circumstances is proportional to the extent of wall 
surface, and that the cubical contents of the flue, including the cham¬ 
bers, has very little influence when the quantity of wall surface has 
undergone any change. These conclusions are fully sustained by 
the experiments formerly made with the two large condensing cham¬ 
bers X and Y, the increase of the cubical contents of the flue, owing 
to their addition, having been almost without influence. 

The amount of dust collected on the bottom of the flue and of the 
condensing chambers was always much higher on the sides than in the 
middle, owing to the fact that after a certain quantity is caught on the 
walls, it falls to the bottom of the flue from its own weight and is 
heaped up there. In the last two campaigns a very much more favor- 


14 METHOD OF COLLECTING FLUE-DIJST AT EMS ON THE LAHN. 


able result was obtained than in the four previous ones, owing to the 
fact that much greater attention was paid to the regulation of the draft / 
by the damper in the chimney, which was kept closed so that the fur¬ 
naces had only just the necessary draft. The material contained in the 
gases had thus much more time to settle on the sides, and that which 
had already settled either there or on the roof was not unnecessarily 
detached from it. The proportional quantity of dust collected upon a 
square meter of wall surface under similar circumstances is neces¬ 
sarily smaller the greater the section of the flue, so that by increas¬ 
ing the wall surface from 10,710 square meters as in the fifth cam¬ 
paign to 22,650 square meters as in the sixth, to 23,791.14 square me¬ 
ters as in the seventh, and to 34,291.98 square meters as in the eighth 
campaign the decrease of the material collected per square meter of 
surface is easily understood. The conclusion was therefore drawn, 
after the results of each period were known, that the wall surface of 
the flue might safely be enlarged, which was accordingly done. Be¬ 
fore discussing the best way to make the final enlargement of the flue, 
it is well to carefully discuss the results obtained in the collection of 
the dust in the latest campaigns. From October 1st, 1880, to August 
11th, 1881, which comprised the sixth campaign of the works, 
14,605,261 kilograms of lead ore containing 6,247,605 kilograms of 
lead were treated in the works.* During this time, 927,483 kilograms 
of dust were collected, which contained 499,875 kilograms of lead. 
Per 1000 kilograms of lead contained in the ores treated, the dust 

contained —— ■ ■— = 80.01 kilograms. The manner in which 

6,24/,605 

this dust settled in the whole flue system is shown in the table 
below. 


* All the determinations of lead which are given in this article have been made 
in the wet way. 








METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 15 


TABLE III. 

Sixth Campaign , lasting from Oct. 1, 1880, to Aug. 11, 1881. 


In the Division. 


Dust. 


o 

Qs 

r Jl 

V-. 

By Square Meter 
of Ground, Side 
and Arch. 

Quantity. 

Lead contained. 

Lead collected 
per 100 square 
meters of wall 
surface. 

Per 1000 Kilos. 

Together. 

© 

Square Meter. 

Kilos. 

Kilos. 

Kilos. 

Kilos. 

I. 

283.02 

68699 

340.70 

23405.97 

8270.08 

II. 

655.05 

43102 

604.13 

26039.34 

3975.23 

III. 

708.12 

53939 

393.80 

21241.56 

2999.71 

IV. 

3602.00 

92225 

479.90 

44285.78 

1229.48 

V. 

708.70 

71187 

606.50 

43174.92 

6092.13 

VI. 

1321.09 

- 65154 

612.70 

39919.85 

3021.74 

VII. 

3383.35 

157874 

608.50 

96066.33 

2839.38 

VIII. 

3088.86 

130950 

556.70 

72899.86 

2360.09 

IX. 

1077.33 

27319 

610.20 

16670.05 

1547.35 

X. 

1165.30 

39658 

593.40 

23533.06 

2019.49 

XL 

1165.30 

32738 

592.70 

19403.81 

1665.13 

XII. 

1009.80 

26922 

512.20 

13789.45 

1365.56 

XIII. 

933.30 

19599 

579.60 

11359.58 

1217.14 

XIV. 

1165.30 

32405 

507.80 

16455.26 

1412.10 

XV. 

1165.30 

28688 

473.60 

13586.64 

1165.93 

XVI. 

933.30 

23713 

467.10 

11086.34 

1187.86 

XVII. 

285.50 

13311 

524.70 

6984.28 

2446.33 


22650.62 

927483 

538.96 

499875.08 

2206.89 


The great decrease of the lead in the dust is very noticeable, it 
is caused by the fact that before cleaning the Hue the dust is usu¬ 
ally set on fire. This is done in several sections at the same time, 
and is easily started with a single match. It is usually done with a 
handful of lighted shavings. It is burned to get rid of the soot, 
the very fine coal, and a part of the sulphur contained in the dust, 
so that the Hues can be cleaned with less difficulty and danger to 
the workmen, and to change the very light dusty material into a 
compact agglomerated mass, which can easily be treated in the 
shaft furnace. This method of burning is successful if the dust 
has accumulated to a considerable thickness, when, as the coke 
and sulphur are burned out, the residue contains the most lead. 
That which is in thick layers, as it is generally the best burned, con¬ 
tains the highest percentage of lead. Whether the layer is thick 
or not is, however, for the purposes of this paper, a matter of no 
consequence, as all that it is necessary to know, is how much lead 
is collected per square meter of wall surface. The table below gives 






















































16 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


the different sections into which it has been found convenient to 
divide the flue for more easy reference. 

Designation of the Different Parts of the Flue. 

No. of 
Sections. 

I. Sheet iron iiue in the shaft furnace-house. 

II. a b. Flue from shaft and roasting furnaces to Station 15. 

III. c d and e/. Flue for the three roasting-furnace houses. 

IV. / g, g h, and h i. Flue from the last roasting-house to chamber V 

V. Condensing chamber. 

VI. k l. Flue from the condensing-chamber to the old chimney. 

VII. I m. Flue from the old chimney to the woods. 

VIII. m n. Flue from the woods to the chamber-house. 

IX. n o, and lower southern division of chamber-house 

X. Upper southern “ " 

XI. Upper northern “ “ 

XII. Lower northern “ “ 

XIII. p q , and lower southern 

XIV. Upper southern “ “ 

XV. Upper northern 

XVI. Lower northern “ “ 

XVII. r s and s t. 


The first section comprises the sheet-iron Hues in the shaft-fur¬ 
nace house through which the shaft-furnace gases are drawn off*. 
The second section is, for the most part, subterranean, and comprises 
that part of the flue which goes from the furnace in the buildings G, 
(Plate I.), and the three southerly roasting-furnaces in the building I, 
towards the chamber h, between Stations 15 and 16. The gases from 
the shaft-furnace and from the three most southerly roasting-furnaces 
are carried off* by it. The third section comprises the mostly sub¬ 
terranean flue, c d, and e /, the southerly part of which enters the 
flue a b, and the northerly part of which, Sec. IV., f g, g h, and hi , 
takes the gases from the roasting-furnaces in the adjacent buildings, 
and comprises all the other stations of the flue up to Station 16. 
At Section V., which is the large chamber, the gases are mixed at 
Station 15 with those coming from the rest of the furnaces. Table 
III., page 15, shows the very large quantity of lead per square 
meter of wall-surface which was collected in Sections I. to V. In 
Section I. the quantity is more than twice as large as in its continua¬ 
tion in Section II., notwithstanding that here the gases from three 
roasting-furnaces are collected. It was to be expected that more 
would be collected in Section I. than in Section II., as the dust me¬ 
chanically carried off* is an important factor in the beginning of the 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 17 


Hues, but that the difference should be so very great must have an¬ 
other cause. As the gases from Section II. and those coming from 
Section 1V. come together in the chamber of Section V., it was 
to.be expected that more dust would collect there. The amount 
collected, however, should, when the conditions remain the same, 
be less than the sum of that collected in Sections II and IX. 
According to the table, however, it is considerably larger. It is 
possible that this, as well as the unexpected quantity collected 
in Section I., is due to the fact that the walls in these two sections 
are entirely above ground, and are therefore easily cooled, while 
those of Sections II., III., and IV. are, for the most part, buried in 
the earth, and will, therefore, sooner or later acquire a temperature 
near to that of the gas. Apart from the condensing surfaces, the 
difference between the temperature of the gases and that of the walls 
of the flue should make a difference in the quantity of gaseous 
metals which can be condensed. The height of the temperature of 
the gases themselves has probablv little or nothing to do with it. 
This, at least, seems to be the undoubted conclusion to be drawn 
from the results obtained in the Sections II. to XVI. When the dif¬ 
ferent sections of the chambers are compared, as in Figs. 14 and 
15, the greater quantity of material collected per hundred square 
meters of wall surface in the upper than in the under part strikes 
the eye at once. This can only be explained by the fact that the 
gases are more thoroughly cooled in the upper than in the lower 
part, the difference between the upper and the lower sections being 
that, with the exception of the partition floor, which is- common to 
both, the side walls of the under part are made of thick masonry 
and are buried in the earth, while the upper one has very thin walls 
which are free. 

Another argument to prove that cooling has an influence over the 
quantity precipitated is shown in the more rapid diminution in the 
upper section than in the lower. While the amount precipitated in 
the upper compartment varies from ‘2019 to 1165 kilos., that in the 
lower varies only from 1547 to 1187. This is undoubtedly caused 
by the fact that the gases in Section X. were at a temperature of 
89° 0., while those in Section XV. were at 64°. The difference be¬ 
tween the highest and the lowest temperature in Section X. was, 
therefore, considerably greater than in Section XV., as was also the 
reduction of their individual temperatures. The reason that the 
precipitation per 100 square meters of surface in Section IX. is less 
by about 813 kilos, of lead than in the previous section, while the 

3 


18 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


precipitation in Section VIII. was only about 479 kilos, of lead less 
than in the one previous to it, is explained by the fact that Section 

VIII. lies with one side and the roof free to the air, and Section 

IX. is entirely buried. The calculation of how much has been col¬ 
lected per 100 square meters in Section XVII. is uncertain, because 
the dust found in the bottom of the chimney was weighed with it, 
and there is no means of ascertaining how far the quantity collected 
there was affected by the inner surface of the walls of the chimney. 

Up to this time reference has only been made to the lead contained 
in the dust. The other components, however, are of interest, especially 
the silver, as its value is always of some importance. The last time 
the flue was cleaned, the dust, according to an assay of 1000 kilos., con¬ 
tained 51.86 grams of silver, so that the total amount of silver con¬ 
tained in the dust was 48 kilos. If, however, the quantity of silver 
which is contained in the lead obtained from the roasted and smelted 
dust is taken as a starting-point, the silver contained in 1000 kilos, 
would be 72.11 grams, or, altogether, 67 kilos., which quantity is, 
therefore, the normal from which all calculations must be made. 
With regard to the repartition of the silver in each section it is the 
greatest nearest the furnace, and then diminishes, at first rapidly, 
but after that very slowly. In the last campaign the amount of 
silver contained in the dust, according to an assay of 1000 kilos., 


was : 

At Station I,.150 grams. 

“ II.50 “ 

III. J ust behind the roasting-furnaces, . . 75 

“ ' IV. .. . 60 “ 

V.45 “ 


From this point the silver diminishes gradually till at the end of 
the flue it is only 30 grams. 

It appears very clear from these assays that in the beginning the 
dust contains a considerable quantity of particles mechanically car¬ 
ried off, which, on account of their weight, can only be transported 
a certain distance. When the draft is stronger they will be carried 
further, and its influence will be shown in the increase of these 
small particles of ore. This explains why it is that in former years, 
when there was no damper in the chimney, there was nearly half 
as much more silver in the flue-dust as now. From the fact that the 
ratio of lead to silver in the flue-dust is different from that in the ore, 
it is certain that in the discussion of this whole question the con¬ 
densation of the volatilized material is by far the most essential con¬ 
sideration. 




METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 19 


The dust contains between three and five per cent, of zinc. In 
genera] it can be said that it is greater in the beginning than at the 
end of the flue. The difference, however, is not very great. The 
antimony contained is between 0.21 per cent, and 0.40 per cent. It 
decreases very gradually in the length of the flue. The dust which 
is deposited on the bottom of the flue often contains L0 per cent, 
more lead than that which is deposited on the arch. This observa¬ 
tion has been confirmed every time the flue has been cleaned. The 
analyses of two samples of dust which was deposited by Station 46, 
more than 1500 meters from the beginning of the flue, is given 
below : 


Analyses. 

i. ii. 


Lead, . 


60.48 per cent. 

67.04 per 

cent 

Z ; nc, . 


3.17 “ 

U 

4.22 

U 

it 

Silver,, 


0.003 “ 

u 

0.003 


CC 

Sulphuric acid. . 


. 14.78 “ 

ii 

14.07 

a 

ii 

Sulphur, 


6.22 “ 

t 

5.42 

cc 

'(( 

Oxide of iron, } 
Alumina, 1 


2.12 “ 

a 

1.00 

(C 

<< 

Carbon, 


8.00 “ 

a 

5.80 

a 

ii 

Antimony, . 


0.42 “ 

a 

0.31 

a 

u 

Arsenic, 


0.24 “ 

a 

0.16 

a 

ti 

Copper, 


trace. 


trace. 



Lime, 


1.15 “ 

a 

0.61 

a 

ii 


Total, . 

. 96.583 “ 

a 

98.633 

a 

i < 


Assav No. I was taken from the arch and No. II from the floor 
directly under it. The difference between these two will not be 
apparent when large masses are considered, for the dust increases in 
depth on the floor, because that which collects on the roof after a 
time gets heavy and falls to the ground on the top of that collected 
there, so that the results obtained bv the analysis of a sample taken 
from a large quantity will be a mean of the two, and will not rep¬ 
resent either the one or the other. 

From these facts it is plain that the most important consideration 
is not that of collecting the particles of ore which are mechanically 
carried off, but of condensing and collecting those which have been 
volatilized and sublimed. Two separate means can be used for con¬ 
densation, and these are the proper application of wall surface, and 
some method of cooling that surface. There is a limit to the pos¬ 
sible cooling of the wall surface, and in anv case this method can 
onlv be useful up to the point where the gases are reduced approxi- 










20 METHOD OF COLLECTING FLU E-DUST AT EMS ON THE LAHN. 


matively to the temperature of the outer air; beyond this point arti¬ 
ficial means of producing the draft would have to be used. How 
far the flue can be cooled will depend on the material used for the 
construction of the walls, and whether the flue itself is more or less 

0 

buried in the ground. 

The limit of methods of construction lies between sheet-iron flues 
suspended in the air or laid on the surface of the ground and ma¬ 
sonry flues buried entirely in the earth. The lowest point to which 
the gases can be cooled will be that which will give the necessary draft 
for the proper conduct of the furnace. The chimney must, therefore, 
be built either upon a high elevation or must itself be sufficiently 
high to produce the draft, or the gases at the foot of the chimney 
must have their velocity increased, either by bringing the gases 
at that point up to the requisite temperature, or by causing the 
air to move by power. In the works at Erns little can be gained by 
the further cooling of the gases, as these at the foot of the chimney 
at Station 47 on the top of the hill have only a temperature of 64° C., 
so that to increase the quantity of dust collected more surface must 
be provided. Since the intercalation of the last two chambers, which 
with their necessary additions have a surface of 8815 square meters, 
it has been found necessary to open the damper of the chimney to 
45°. Formerly it could only be opened with safety to 27°. There 
is little or nothing to be done further to increase the draft except to 
open the damper entirely, or to increase the height of the chimney. 
This must be done when a second condensing-chamber building like 
those at X and Y, is constructed as it must be. The cost of this 
construction would be 64,486.29 marks; according to the last ex¬ 
periments that were made, this sum would be repaid at the latest 
inside of three years. As, however, all that is necessary now is to 
increase the wall surface, this can be done more quickly and eheaplv 
by placing sheet-iron plates in the flues already constructed. This 
system was tried in Section XVI. from August 28th to December 
24th, 1881. Four rows of sheet iron, No. 22, 100 meters long and 
one wide were hung in the flue. Taken together they represented 
800 square meters surface; the collective wall surface of this 
divison was, therefore, increased from 933 to 1733 square meters. 
The quantity of lead contained in the ore and in the dust at this 
time was 3,028,565 kilograms. In the previous campaign of the 
6,748,816 kilograms of lead in the ore and dust which was treated, 
there were collected in Section XVI. 23,713 kilograms of dust. 
It was, therefore, calculated that with the increased wall surface 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 21 


from this arrangement of thin plates, 19,766 kilos, would be col¬ 
lected in this. The amount actually collected was 18,800 kilos, 
which was somewhat higher in lead than that collected in the pre¬ 
vious experiment. The results of these experiments were so satis¬ 
factory that the number of plates was increased to six, as shown 
in Fig. 16. The quantity thus collected was so very large that 
in some of the sections of the main flue, notably in Figs. 11, 12, 
and 17, vertical plates 10 millimeters apart were introduced. As 
this method of construction costs only about one-tenth as much as 
the same amount of wall surface made with masonry, and allows 
of regaining more flue dust than the construction of long flues and 
condensing chambers without it, a patent for the improvement has 
been taken out in the name of the Ems Lead and Silver Works,* 
which has proved not only useful for metallurgical but also for chemi¬ 
cal and other manufacturing works where metals are likely to be 
volatilized. It is also probable that its use will be found advan¬ 
tageous in the manufacture of zinc white, the treatment of ores of 
mercury and other volatile substances, where the main object of the 
treatment is the condensation of the volatilized metals. 

After the first trial the hanging plates were introduced into Sec¬ 
tions VI., VII., and VIII., a section of which is shown at Fig. 11. 
They were then introduced on a much larger scale in Sections V., 
VI., VII., VIII., and IX., as shown in Figs. 16 and 17. 

The method of hanging-in the sheet-iron consists in placing a 
rectangular bar of iron, which has been pierced with the requisite 
number of holes, on its edge, in the spring of the arch, if the arched 
form of flue is used, or at the proper height in the rectangular ones. 
This bar is twisted flat at its ends so as to enter the wall about 3 cm. 
Iron pins, 10 cm. between centres, are driven into the holes, pro¬ 
jecting 3 to 4 cm. on both sides. A piece of iron, D, Fig. 17, 
bent to form a hook, is riveted upon the ends of each sheet, so 
that it simply drops on to the pins, and hangs at each end supported 
in a vertical position. So arranged, the sheets can be put up or 
taken down with the least possible trouble. To simplify the con¬ 
struction, a punching machine is used which pierces two holes at once 
in the sheet-iron at the proper distance from the edge. The iron which 
forms the hook L, Fig. 17, is punched in the same way. The riveting 
is done with two or three blows of the hammer. When the sheets are 
hung upon the pins they fill up the flue, and have between them in 

* Jan. 13th, 1881, Germany, No. 17,513.—March 12th, 1882, Hungary, No. 8454- 
—October 20th, 1881, England, No. 4590.—April 3d, 1882, Spain, No. 2232.—March 
12th, 1882, Austria, No. 3723.—April 24, 1883, United States, No. 276,386. 


) ) 


> > 1 




22 METHOD OF OOELEOTTNG FTJTE-DD.ST AT EMS ON THE LATIN". 


the direction of the length of the flue only the thickness ot the iron 
bars on which they rest. These sheets do not make any perceptible 
reduction of the total volume of the flue, but they increase the con¬ 
densation-surface enormously. 

Fig. 16 shows the arrangement of Fig. 11 when only six sheets 
were used ; Fig. 17, the arrangement of the same flue when 1 7 are 
used. A vacant space is left, as C F C E in Fig. 17, to show the 
method of hanging-in the sheets on the iron bars L, as well as the 
method of supporting the partitions on the bottom ot the flue. In 
order not to impede the draft these plates must be placed parallel to 
its direction, and be as thin as possible. It will also be necessary 
to place them as nearly vertical as possible so that when the dust con¬ 
denses upon them, after it has attained a certain thickness, it will 
fall down upon the floor of the flue and remain there. In order to 
bring the quantity of dust which settles up to a maximum, the ma¬ 
terial which has once been condensed and brought to rest, should 
remain, as far as possible, where it was arrested, or if allowed to 
move should fall vertically on to the floor, and remain there, so that 
it would no longer be possible for it to be caught up again by the 
draft and be carried up the chimney. The simplest and cheapest 
means of effecting this, is to make partitions, about 50 cm. high and 
nearly touching the vertical sheets, across the bottom of the flue, 
as is shown at E, Figs. 16 and 17. Every five or six meters, or less, 
partitions are made at right angles to the direction of the draught. 
In the first experiments they were made of stone, laid up dry, as 
shown at E, Fig. 16. It has been found best, in the more recent 
constructions, to make them of sheet-iron, as is shown at E, Fig. 
17. The sheet-iron is supported in wrought or cast-iron feet C, to 
which it is attached by bolts. It is easily set one side when the flue 
is cleaned, or can be quickly removed from the supports if it is for 
any reason necessary to do so. This kind of construction has the 
advantage of not only being easily removed and replaced, and of 
being quickly repaired, but it is never in the way. The dust col¬ 
lected is purer, because there is no chance of having small particles 
of broken stone mixed with it. This method of using plates for in¬ 
creasing the condensing surface costs very little, as any kind of sheet- 
iron can be used. The cost of putting in is only 21 pfennigs. By 
the ordinary construction one meter of the length of the flue gives 
only 8.22 square meters of surface; altered in this way, the same 
length gives, with six plates, 65 square meters of surface, and with 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 23 


seventeen, 184 square meters, while its volume is lessened only a 
very little. 

In all parts of the flue where these sheet-iron plates have been 
placed, enormous quantities of dust have been found every time 
the flue has been cleaned, the quantity being greater as the surface 
was larger. As no such quantities have been found before, and as 
the increase in quantity is directly in the ratio of the increase of the 
surface, there is every reason to believe that it will prove effectual 
up to a limit which has not yet been ascertained. The quantity of 
dust collected, especially in the last section of the flue, was verv large. 
Usually, but very small quantities can with certainty be counted on 
in that position. It seems probable that by the use of a suitable con¬ 
struction, a still larger part of the dust can be collected, and most 
of that which is now lost saved, thus diminishing the expenses and 
increasing the receipts of the works very considerably. 

With regard to the number of sheets to be introduced in each 
section of the flue to produce a maximum effect, it may be said the 
more the better, provided they do not interfere with the draft. It 
has been found best to use very thin sheets, and to concentrate them, 
as far as possible, in a small portion of the flue, rather than to 
scatter them throughout it, or over a very large part of it, as the 
cost of construction will for this reason be less. Whether more than 
seventeen or eighteen sheets can be used in a flue of the size of Sec¬ 
tions VI., VII., VIII., and XVII., or whether, in a larger flue, it 
will ever be found advantageous to hang them closer than 0.01 meter 
apart remains to be seen. Up to the end of the ninth campaign they 
were hung 0.01 m. apart. So much dust was then collected in Sec¬ 
tion VI. by this method that the flues became choked and the fur¬ 
nace had to go out of blast. The plates can only be hung so close 
together at the end of the flue without endangering the length of 
the campaign, unless auxiliary flues are provided, as has been sug¬ 
gested, so that the sections may be cleaned whenever desirable by 
turning the gases into the auxiliary flue, and when that is full, back 
again, without stopping the works. No general rule can be given 
either for the number of plates nor for their relation to the width oi 
the flue, for the quantity of gases passing through it, or the quantity 
of sublimed material likely to be contained in the gases. They not 
only differ in the different works, but they are often different in indi¬ 
vidual parts of the same works. The use of sheets thinner than 0.675 
mm. would give more surface for the same volume, but they would 
have to be supported differently, as they would be likely to be moved 


24 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


from side to side by the blast. If they were bung from the top, 
there would be danger of their meeting at the bottom, and thus ob¬ 
structing the draft. To support them in more than one place would 
naturally increase the difficulty of using them as well as the cost. The 
introduction of three or four more in the same space would largely 
increase the surface, but could not be done advantageously it it in¬ 
creased the difficulty of manipulation, or the cost at the same time. 
More plates would then have to be used in the length of the Hue. 
The cause of failure, if any, in the system would be the increase of 
friction-surface, and this limit would have to be found in every 
case. Whether it will be wise to increase the section of the Hue in 
order to introduce more plates can only be ascertained by experi¬ 
ment. When careful records of the action of each shape of Hue, 
where the plates are used, have been made, the ledger account will 
soon show which form of flue it is most economical to adopt. 

The material used for the plates may be different according to the 
temperature which obtains in that part of the flue where they are 
to be used. Thin sheet-iron seems to be the best, which need not even 
be new. The worn-out iron sieves of the jigs from the dressing- 
works can be used, and where the temperature is very low, as in the 
last section of the flue, next the chimney, on the hill, pasteboard 
can be used. Combustible material cannot, of course, be used where 
the flue is to be fired. It would be best, however, to make experi¬ 
ments iu each case as to what material will be most suitable. 

Whether these plates can be best hung up or fixed permanently, 
as well as the best way of carrying out the rest of the system, must 
be determined in each special case. It will generally be found best 
to have them easily removable, to facilitate the firing of the dust 
(which is peculiar to the works at Ems), as well as to facilitate the 
cleaning of the flue. 

In England a patent was taken out in the year 1880 for plates 
which are put in horizontally. The object of this invention is to 
collect the dust by making the draft as slow as possible and causing 
the particles arrested to fall the shortest possible distance. To di¬ 
minish the velocity of the gas, it is passed from the main flue into 
very large condensing chambers, built at the side of the main flue 
and divided by parallel walls into a large number of flues, in which 
iron plates are placed horizontally and close together the whole width 
of the flue, so as to make the fall of each particle as small as possi¬ 
ble. There is no doubt that so far as the collection of the dust is 
concerned, this system will do it rapidly, but the system itself is 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 25 


/ 


both defective and expensive. As the dust is accumulated in hori¬ 
zontal layers, the volume of the flue is rapidly diminished, and as 
there is no provision made for arresting the dust where it falls, the 
amount of surface must always be a maximum. It will take a long¬ 
time for such large condensing chambers to cool down so that the 
men can enter them, so that much time will be lost before they can 
be cleaned. The danger to the men by bringing them in contact with 
this impalpable dust, which is set in motion every time one of these 
layers is removed, while cleaning the flue, will effectually prevent 
the general introduction of this method. 

The seventh campaign lasted 200 days, the details of which are 
given in table IV below. 


TABLE IV. 

Seventh Campaign , lasting from Aug. 28th, 1881, to March 24 th, 1882. 


There was collected from the 28th of August, 1881, to 24th of March, 1882 

• 


In Section. 

Quantity of Dust. 

Quantity of 
Lead per 100 
Square Meters 
of Wall 
Surface. 

No. of Section. 

Square Meter of 
Ground, Side. 
Wall, and Arch 
Surface. 

Weight. 

Lead Contained. 

Square Meter. 

Kilos. 

Per 1000. 
Kilos. 

Total Lead. 
Kilos. 

Kilos. 

I. 

283.02 

75449 

401.163 

30267.38 

10694.43 

II. 

655.05 

8471 

609.300 

5161.38 

787.93 

III. 

708.12 

12392 

433.552 

5335.40 

743.46 

IV. 

3602.00 

75265 

443.316 

33336.22 

926.32 

V. 

1049.20 

30171 

619.047 

18677.26 

1780.14 

VI. 

1321.09 

35257 

628.199 

22148.41 

1676.52 

VII. 

3383.35 

110576 

626.400 

69464.81 

2047.22 

VIII. 

3088.86 

74050 

624.000 

46207.20 

1495.93 

IX. 

1077.33 

27150 

669.106 

18166.22 

1686.23 

X. 

1165.30 

251-50 

646.300 

16254.44 

1394.87 

XI. 

1165.30 

24600 

638.300 

15702.18 

1347.48 

XII. 

1009.80 

22500 

615.330 

13844.92 

1371.05 

XIII. 

933.30 

21950 

623.396 

13683.54 

1466.15 

XIV. 

1165.30 

20950 

547.900 

11478.50 

985.02 

XV. 

1165.30 

26800 

577.600 

15479.68 

1328.38 

XVI. 

1733.30 

33100 

595.979 

19726.91 

1138.11 

XVII. 

285.50 

8900 

590.907 

5259.07 

1842.06 


23791.12 

632731 

568.999 

360028.52 

1513.27 


The value of the 632,731 kilos of dust is 88,542 marks. If the 
seventh campaign had lasted 350 instead of 200 days, the corre¬ 
sponding value would have been 1,107,296 kilos of dust, worth 
155,019 marks. 


4 






































26 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


The sixth campaign lasted 314 days. During this time the ore 
treated contained 6.247,605 kilos, of lead, the details of which are 
given in Table III., page 15. The seventh campaign lasted only 
200 days, and the ore treated contained 4,245,303.21 kilos, of lead. 
In order to make the comparison between the two the amounts given 
for the seventh campaign will have to be increased in the ratio of 
4,245,303.21 : 6,247,605. This has been done in table V., below: 


TABLE V. 

The Seventh Campaign increased for the purpose of comparison with'the 

Sixth Campaign. 


There was collected from the 28th of August, 1881, to 24th of March, 1882 

Quantity of 
Lead per 100 
Square Meters 
of Wall 
Surface. 

In Section. 

Quantity of Dust. 

No. of Section. 

Square Meter of 
Ground, Side, 
Wall, and Arch 
Surface. 

Weight. 

Lead Contained. 

Square Meter. 

Kilos. 

Per 1000. 
Kilos. 

Total Lead. 
Kilos. 

Kilos. 

I. 

283.02 

111030.75 

401.163 

44541.43 

15737.92 

II. 

655.05 

12465.92 

609.300 

7595.48 

1159.52 

III. 

708.12 

18236.06 

433.552 

7906.28 

1094.04 

IV. 

3602.00 

110759.97 

443.316 

49101.67 

1363.17 

V. 

1049.20 

44399.64 

619.047 

27485.46 

2619.65 

VI. 

1321.09 

51884.20 

628.199 

32593.60 

2467.17 

VII. 

3383.35 

162723.64 

626.400 

101930.09 

3012.69 

VIII. 

3088.86 

108971.98 

624.000 

67998.52 

2201.41 

IX. 

1077.33 

39953.94 

669.106 

26733.42 

2481.46 

X. 

1165.30 

37010.74 

646.300 

23920.04 

2052.69 

XI. 

1165.30 

36201.36 

638.300 

23107.33 

1982.95 

XII. 

1009.80 

33111.00 

615.330 

20374.19 

2017.64 

XIII. 

933.30 

32301.62 

623.396 

20136.70 

2157.59 

XIV. 

1165.30 

30830.02 

547.900 

16891.77 

1449.56 

XV. 

1165.30 

39438.88 

577.600 

22779.90 

1954.84 

XVI. 

1733.30 

48709.96 

595.979 

29030.11 

1674.84 

XVII. 

285.50 

13097.24 

590.907 

7739.25 

2710.78 


23791.12 

931126.92 

568.999 

529865.24 

2226.93 


It is to be noticed that in Section V., which is the condensing cham¬ 
ber at Station 15, shown at Fig. 10, the quantity of wall surface has 
been increased from 708.10 square meters to 1049.20 square meters, 
and that of Section XVI., which is the lower northerly part of the 
condensing chamber Y, at the top of the hill, Fig. 12, from 933.30 to 
1733.30 square meters. Section V. is very near the furnaces. Sec¬ 
tion XVI. is at the foot of the chimney. 

Table V. shows that there has been a very large increase in the 







































METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 27 


quantity of dust collected, except in Sections V., VI., VIII., X., and 
XIV., where the quantities are in round numbers 26,000, 13,000, 
3000, 2500 kilos, less. The total quantity collected is, however, 
greater than in the sixth campaign, and almost in direct proportion 
to the increase of wall surface. But in every case where there is a 
diminution, except in Section XIV., there is an increase in the quan¬ 
tity of lead per 1000 kilograms. The quantity of lead per square 
meter of wall surface is less in Sections V., VI., and VIII., and 
slightly more in Sections X. and XIV. The total quantity is, how¬ 
ever, enough more to justify close attention. 

It would naturally have been thought best, as soon as the practi¬ 
cability of this method of using iron plates had been proved, to have 
hung the whole flue full of them, but as no sufficient data had been 
collected as to how far the draft would be affected by it, it was done 
very gradually. Before the seventh campaign, in August, 1881, 
1140 square meters were put in. In March, 1882, before the eighth 
campaign, 10,450.86; and after the eighth campaign, in September, 
1882, 13,055.35 more, so that up to this time there were 24,471.60 
square meters of sheet-iron plates hung in the flue. An accident, 
which happened in the summer of 1882, made it necessary to do 
away with the upper part of the condensing-chamber building, which 
includes Sections X., XI., XIV., and XV., Figs. 14 and 15, as the 
roof was no longer tight. The flue itself had then 18,060.01 square 
meters of wall surface; this, with the 24,471.60 square meters of sheets, 
made 42,531.61 square meters of available condensing surface. The 
sheet-iron plates introduced cost 18,108.98 marks. If this amount 
of surface had been introduced by means of a masonry canal, such 
as is shown in Fig. 9, the square meter of which costs at least 11.71 
marks, it would have amounted to 286,562.44 marks. There was 
thus saved by the use of the iron plates a sum of 268,483.46 marks. 

It was a matter of some interest to ascertain whether the draft 
had not been diminished by the enormous friction surface which 
has been added in the flue by the very large amount of surface 
introduced into it. As the entire flue during the three weeks that 
the works were obliged to stop for these repairs, was very much 
cooled, it was found that at the time the works were put into blast 
again, there was such a very weak draft that it was necessary to put 
a fire at the bottom of the chimney on the top of the hill. After 
three days’ use of it the draft was sufficiently strong to make it no 
longer necessary. The damper in the chimney is now not entirely 
open. Little by little it will be brought back to its former angle. 


28 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


With regard to the temperature in the flues, the gases escaping from 
the chimney in the normal working of the establishment have a 
temperature of between 60° and 70°. Witli regard to the quantity 
of lead contained in the dust, setting it on fire undoubtedly dimin¬ 
ishes the quantity more or less, but that upon the arch, which 
afterwards falls to the ground, does not contain as much as that 
which collects on the bottom of itself. Taking the sample for the 
assay is on this account very difficult, and mistakes are very apt to 
be made, when the fact of the dust collecting in layers of variable 
richness, is not taken into account. The assays taken at the end of 
the seventh campaign were in any case more nearly correct than 
those taken at the end of the sixth. 

The sheet-iron plates which have been hung have lasted extremely 
well. i7ot one of them has as yet been damaged, and it seems more 
than likely that they will last at least five years. The only danger 
appears to be from dampness which would cause them to rust, and 
this can only be avoided by confining the places in the flue where 
they are hung to such a distance from the furnaces that it is certain 
that all the dampness will have previously been condensed out of the 
gases, and by properly draining the surface so that no moisture can 
collect in it from the outside. By this system it is possible to collect 
the whole of the dust in a small part of the flue near the works, and 
thus save a large amount of transportation of the material collected, 
while at the same time diminishing by so much the loss consequent 
on carrying it. This loss by transportation will, of course, be re¬ 
duced to a minimum when the dust is agglomerated. 

Cleaning the flue necessitates, at certain intervals, a stoppage of the 
works, so that only those places are frequently cleaned in which 
the sheet-iron hangs, while the flue itself is cleaned at longer inter¬ 
vals. In those places where a stoppage of the works is impossible, 
two flues filled with sheet-iron plates can be built side by side 
in the most convenient situation, so that either one may be connected 
or cut off entirely from the main flue, according as they have been 
cleaned or are to be cleaned, without stopping or even hindering the 
work of the furnace at all. 

In order to ascertain how far this system of enlargement of the 
flues can be carried without danger, and how far the wall surface 
can be increased, and what is the limit at which it would pay, a 
table of the results of the sixth and seventh campaign at Ems is 
given below in Tables VI. and VII., taking as a basis Table III., 
page 15. 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 29 


The sixth campaign was 314 days. I n order to see the results more 
clearly the calculation has been made as if the campaign had been a 
year of 350 working days and 15 days of rest for cleaning out the flues. 
The quantities given in Table III will, therefore, be found altered 

in the ratio of 314 to 350. The value to the works of 100 kilo- 

* 

grams of the dust collected is calculated on the supposition that the 
price of 100 kilograms of lead is 29 marks, and that the loss by the 
treatment is five per cent., and that the cost of treatment including 
transportation is 2.4 marks per 100 kilograms. The value of the 
silver is included in the calculation. 


TABLE VI. 


Sixth Campaign , reduced to 350 days. 




There was Collected 


— 

— 

Value of the 
Dust per 100 sq. 

In 

the Section 


Dust. 








Meters of Wall 


By Square Meter 



Value. 


Surface. 

<D 

of Ground, 

Quantity. 

— 






3 

Side aud Arch. 


Per 100 Kilos. 

Together. 



£ 

Sq. Meters. 

Kilos. 

Marks. 

Pfen'gs. 

Marks. 

Pfen’gs 

Marks. 

Pfen’gs. 

| 

VT. 

1321.09 

726240 

15 

24 

11067 

90 

' 837 

1 84 

VII. 

3383.35 

175974 

15 

1 o 

lo 

26624 

87 

786 

95 

VIII. 

3088.86 

145963 

13 

65 

19923 

95 

645 

04 

IX. 

1077.33 

30451 

15 

17 

4619 

42 

428 

76 

X. 

1165.30 

44205 

14 

73 

6511 

40 

558 

74 

XI. 

1165.30 

36491 

14 

71 

5367 

83 

460 

65 

XII. 

1009.80 

30009 

12 

46 

3739 

12 

370 

27 

XIII. 

933.30 

21846 

14 

26 

3115 

24 

333 

76 

XIV. 

1165.30 

36120 

12 

26 

4428 

31 

379 

99 

XV. 

1165.30 

31977 

11 

35 

3629 

39 

311 

42 

XVI. 

933.30 

26432 

11 

02 

2912 

81 

312 

12 


16408.23 

652092 

14 

10 

91940 

24 

560 

i 34 , 


In order to compare the results of the seventh campaign with 
those of the sixth, the same calculation has been made which is 
given in Table VII., below: 















































30 METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 


TABLE VII. 

Seventh Campaign, reduced to 350 days. 


There was Collected 


Id Section 

Dust Collected. 

Value 

of the Dust per 




| 




1UU sq re 

meters 


Per square meter 



Value. 


of 

U 

of Ground Wall 

Weight. 





Wall Surface. 


and Arch Sur- 







2 

3 

face. 


Per 100 Ks 

Total. 




a 

Square Meters. 

Kilos. 

Marks. 

Pfeng’s 

| 

Marks. 

Pfng. 

Marks. 

Pfeng’s 

VI. 

1321.09 

57830.13 

15 

90 

9194 

99 

696 

15 

VII. 

3383.35 

181371.77 

15 

76 

28584 

19 

844 

85 

VIII. 

3088.86 

121460.17 

15 

69 

19057 

10 

616 

96 

IX. 

1077.33 

44532.66 

16 

93 

7539 

38 

699 

82 

X. 

1165.30 

41252.17 

16 

37 

6752 

98 

579 

50 

XI. 

1165.30 

40350.04 

16 

00 

6456 

00 

554 

02 

XII. 

1009.80 

36905.52 

15 

40 

5683 

45 

562 

83 

XIII. 

933.30 

36003.39 

15 

64 

5630 

93 

603 

34 

XIV. 

1165.30 

34363.14 

13 

59 

4669 

95 

400 

75 

XV. 

1165.30 

43958.58 

14 

41 

6334 

43 

543 

60 

XVI. 

1733.30 

54292.12 

14 

95 

8116 

67 

468 

28 


17208.23 

692319.69 

15 

60 

108020 

08 

627 

72 


In these tables Sections I. to V., both because they have given ex¬ 
ceptionally favorable results and because the gases are only collected 
in the main flue at Section V., have been omitted. Section XVII., 
as designated after Table VII., because of the unknown effect of the 
wall surface of the chimney, is also left out. 

To make these results of the sixth and seventh campaigns appa¬ 
rent to the eye they have been graphically represented on Plate III. 
The abscissas indicate the number of square meters of wall surface 
contained in every section ; the ordinates represent the total value 
of the dust collected in each section and also the value per 100 
square meters of wall surface. Each section is thus represented by a 
rectangle which gives a graphic representation of the total quantity of 
wall surface contained in each, and the value of the material collectek. 
These are printed on the middle line of the rectangle representing 
each section. In each rectangle there are two figures giving the value 
of the dust collected, the upper one being for the sixth and the lower 
for the seventh campaign. The lines of the sixth campaign are rep¬ 
resented in full while those of the seventh are represented as dotted. 
The ends of the middle ordinates are joined, making a zigzag line 
which is quite different for each one of the sections in the two cam¬ 
paigns; a curve representing these lines has been given, showing 





















































METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 31 


the value of the dust collected for both the sixth and seventh cam¬ 
paign. 

During the seventh campaign no change in the quantity of wall 
surface was made except in Section 16 where the wall surface was 
increased from 933 square meters to 1733 square meters. It is very 
remarkable that while between these two campaigns no change 
in the quantity of wall surface has been made except in Section 
XVI, all the weights and values have been altered by this single 
change; and that while the flue has been made very much shorter 
by the cutting out of the condensation-chambers X and Y, the wall 
surface has been so much increased by the addition of sheet-iron 
plates that with the exception of Sections VI and VIII the value has 
in every section been increased, while the total value has been very 
largely increased, which is shown by the curve representing Section 
XVI in the seventh campaign being very much higher than that of 
Section XVI in the sixth campaign, making the total value of the dust 
collected in this Section more than three times what it was in the 
former campaign while the surface has not been quite doubled. This 
shows beyond doubt that the quantity of material collected is pro¬ 
portional to the extent of wall surface, and that the cubical contents 
of the flue itself is of importance only as it allows of a maximum 
amount of surface in the shape of plates being introduced within it. 
It is also to be remarked that while the curve in the seventh cam¬ 
paign is much flatter it commenced in Section VI with less value, and 
there seems, therefore, no doubt whatever that this method which 
is not only cheap, so far as the installation is concerned, is also by 
far the most effective of any which has yet been devised for the collec¬ 
tion of flue-dust, and notably for the condensation of the volatilized 
material. It is to be noticed that there are three separate causes 
which will make the curve flatter. The first of these is the decrease 
in value, owing to the complete separation of the particles mechani¬ 
cally carried off*; the second is the decrease in value, owing to the 
reduction in temperature; and third, the decrease in the value of 
the gases, owing to the separation of the metallic particles held in 
suspension. 

As is shown by the results, the first cause, that is the separation of 
the particles carried off* mechanically, acts within a very short dis¬ 
tance from the furnace, so that by the proper construction of the 
condensing plates, nearly the whole of the ore particles will be 
separated from the gases, not far from the furnaces themselves. 
There will remain then in the gases only the volatilized metals. 


32 METHOD OF COLLECTING FLUE-DUST AT EM8 ON THE LAHN. 


Some of the causes of the difficulty of the separation of them from 
the gases have been already discussed. It appears, however, that 
the curve might easily become a straight line if it were possible by 
the introduction of an infinite quantity of surface to condense the 
whole of the dust. It would seem from the discussion of these two 
curves that the influence of the reduction of temperature was not 
as great as it appeared to have been from the experiments made in 
the sixth campaign. It will, however, probably be found expedient 
on account of repairs to still further disengage the sides of the flue, 
both for convenience of repairs and convenience of access. 

It appears from Table I., page 10, that the cost of the construc¬ 
tion of a square meter of wall suface in the flat flue of Section 4, ex¬ 
clusive of the cost of the ground was 9.976 marks. This calculation 
is made on the supposition that the cost of the ground for the square 
meter of wall surface was 0.44 marks; one square meter will, there¬ 
fore, cost 10.20 marks, and 100 square meters will cost 1020 marks. 
In all these observations the condensing chambers X and Y, since 
they have cost so much for repairs, have been left out of the con¬ 
sideration altogether as defective, are not taken into the calculation. 

The square meter of wall surface made of new sheet iron, No. 22, 
including the cost of erection, will not cost more than 0.75 marks. 
One hundred square meters would, therefore, cost 75 marks. In 
making up the cost of these two methods of getting surface as is 
shown upon Plate III., 10 per cent, of the cost of construction has 
been charged for the sinking fund of the masonry walls, while for 
the sheet-iron surface, 20 per cent, which is a very large charge, is 
made. The yearly charge, then, for the sinking fund for the 100 
square meters of masonry surface, would be 102 marks, while for the 
surface obtained by hanging in the sheet-iron plates it would only be 
15 marks. The difference between the two is shown very decidedlv 
in the lines representing the cost, Plate III. From the experiments 
which have already been made since the introduction of these sheet- 
iron plates in the Hues, 20 per cent, seems to be a very exorbitant 
charge, although made very high purposely, in order to make the most 
disadvantageous comparison between the two systems. No percepti¬ 
ble alteration or wear has been shown after a use of five years, so 
that if less than 20 per cent, is charged, the line would go still lower 
than it now does, and it would seem to be the natural conclusion 
that the cheapest method would be to build short, large flues in 
which the maximum of wall surface was obtained by the intercalation 
of these plates. All the experiments made up to the present time 


METHOD OF COLLECTING FLUE-DUST AT EMS ON THE LAHN. 33 


fully justify the conclusion, that not only is this the most economical 
method of saving a quantity of material which has hitherto gone to 
profit and loss, because it was supposed to be impossible to save it, 
but that it is also possible to reduce very largely the cost of the 
works by increasing the wall surface indefinitely at a very cheap 
rate. The most remarkable fact relating to these experiments is 
this, that by almost doubling the wall surface in the last section of 
the flue which is furthest removed from the works, where there was 
no probability that any material mechanically carried off by the gas 
would be still retained suspended in it, there is such a large amount 
of value obtained from the dust. This can only be attributed to 
the fact that the metallic material which is volatilized, and which is 
collected with such great difficulty, has been carried to that point 
and condensed there, and that without this increase of wall surface 
this large amount would have gone up the chimney and been entirely 
lost. It seems, therefore, that not only in all works where the flue- 
dust contains value should especial attention be given to collecting 
it, but that the quantity of metal which is actually volatilized, merits 
special attention. 

When the values which represent the different sinking funds for 
the year are transferred to Plate III., and compared with the 
curve which shows the value of the dust collected in the different 
divisions of the flue, and these data are also compared with the very 
great value of the flue-dust collected, it is a matter of surprise that 
the collection of flue-dust in metallurgical works does not appear to 
have attracted more special interest than it has done, if only on ac¬ 
count of its pecuniary importance. 


5 





















! , • 











1 ■ vjf| 




Vtl 





























































> i 


Trams, of tUie lamer. Institute of Miming Engineers. Vol, XI 


Egleston.—Plate I 




PROFILE OF THE FLUE. 


200 


300 


























































































Transactions of tine American Institute of Mining Engineers. Vol. XI, 


Egleston.—Plate II, 







Fig-5 


Fig-6 


Fig-7 


Fig.8 


Fig.11 


Fig-12 


Fig-15 


Fig.10 


Fig.13 


SECTION C. D. Fig-16 


Scale. 1:90 


A. B? 







































































































































































































































































Transactions off tine American Institute of Mining Engineers. Vol. XI. 


Egleston.—Plate III, 


Marks S5u. 


Marks 800 


Marks 750 


Marks 700_ 


Marks 650_ 


Marks 600_ 


Marks 550_ 


Marks 500. 


Marks 45CL 


Marks 400. 


Marks 350- 


Marks 30CL 


Clarks 25CL 


Marks* 150. 


Marks 10Q_“ 


Marks 50_ 

40l 

80. 

2(L 

1CL- 

_ 0 


GRAPHIC REPRESENTATION 

of the 

VALUE OF THE DUST COLL ECTED 
and 

OF THECOSTOF DOING IT. 



Total | value 
of the dust!collected 
11067 iliarks 
9105 nlarks 


~ € c 

c ~b ; a5 

“ - O j j* 


Total l value 
of the dust!collected 
26624 Quarks 
28534 fuarks' 


« o " 

-o a I O. «* 
•** g g 

*0 ~ n“ i 3 a 

2 co iggi 

ji 3 a3 

> -o S.;e- X> 

I 

I 

I 


Total 
of the dust 
19923 I 
19057 l 


value 

collected 

arks 

arks 


Total ;value 
of the dust) collected 
4619 iliarks 
7539 marks 


Totalivalue 
of the dust collected 
6511 ijmrks 
6753 marks 


°c°o 


a 3 


■ 5 ? 

°Pl 


5 

s lies? 


”5 a;3 3 


. 3 ® |e< 


COST 0F THE SINKING FUND’AND INTEREST OF THE CHEAPEST FLUE 10^ OF THE COST OF CONSTRUCTION. 


1“ 


• Totalivalue 
of the dust collected 
5367 tjiarks 
6456 marks 




COST 9 F THE SI 4KING FUND AND INTEREST OF THE HANGING SHEET-IRON PLATES 20%jOFTHE COST OF CONS 


I 

TRUCTIpN. 


Totalivalue 
of the dust.collectcd 
3739 marks 
5683 .iuarks 


£ <3 £ I . 
- « g j.S.3 
•s^siss 
S8||S8, 

* 3 fe ! 2 S 

ra a.' ec “3 


5631 -jnarks 

si 

223 tf 2 


sfgiss 

In i_ ! oo'ec' 
3 v ro o 
►>-C 0.|C0 5£> 


. Totalivalue 
of the dust collected 
4428 ijiarks 
4670 marks 
: 

tj «2! 

•2 g ® 

'Ztt ! 3 3 

Q) C § I *° 

« = 53'?o 
t>-o a, co^j 1 


Total] value 
of the du^t collected 
3629 iliarks 
6334 iliarks 


1000 Mtr. 

-t^ 


3000° Mtr. 
-1-- 


5000 Mtr. 


6000 Mtr. 

- 1 - 


1000!) Mtr. 


12000 Mtr. 


13000 Mtr. 


14000 Mtr. 


16000 Mtr. 


17000 Mtr. 18000 Mtr. 

















































































































































__ • 

































' 














































































